1. Field of the Invention
The present invention relates to a coat-finishing method for polyester woven and knitted fabrics which does not have migration problems.
2. Description of the Prior Art
Generally, nylon and cotton fibers and woven and knitted nylon and cotton fabrics, are base materials which are treated with coatings, such as, water proofing, moisture permeable water proofing, water-repellent and moisture permeable water proofing, flame-retardant and anti-melting, water-repellent and water proofing. Such coated fabrics are widely used as apparel and for industrial use.
Recently, a coat-finishing method for polyester woven and knitted fabrics has been developed because of the excellent mechanical properties, dimensional stability, weather resistance, aesthetical properties and low prices of polyester fiber.
However, these coat-finished, woven and knitted polyester fabrics suffer from problems. For example, the problem of staining white or light color fabrics adjacent to the coat-finished fabrics exists, due to the migration of the coating layer during the processes of coat-finishing, sewing, handling, storage and use.
Accordingly, the coat-finishing of polyester woven and knit fabrics is not performed on light color fabrics or is done with little regard to the migration problem.
Dyeing of polyester fiber by disperse dyes can be summarized as a process of inserting dye into the polymer chain by physical affinity, without chemical bonding between the fiber and the dyestuff.
Since the disperse dye migrates easily, especially to the coating layer, the quality of goods is lost and the migration from fiber to coating layer during sewing, handling, storage and use and from the coating layer to fiber goods adjacent to the coated fabrics occurs easily and results in staining.
To alleviate the above-mentioned migration problem of coat-finished fabrics composed of polyester fiber, a number of coating methods have been suggested to date.
Prior art solutions to the coating migration problem are summarized as follows.
Firstly, Japanese laid-open patent publication No. 61-252383 discloses preventing migration by using a special process of wetting with a tannin compound before or after the coat-finishing process.
Secondly, it is disclosed in Japanese laid-open patent publication No. 61-19876 that migration may be prevented by using N-alkoxydimethylated polyamide as a coating resin.
Thirdly, there is a method for formation of a special coating layer which prevents migration by coating a highly hydrophilic amino acid resin on an existing coating layer as shown in Japanese laid-open patent publication No. 60-39479.
Fourthly, performing the coat-finishing process after the dyed fabric is treated with a low temperature plasma at constant pressure is shown in Japanese laid-open patent publication No. 1-207475 and 3-45782.
In addition, a method for coating is disclosed wherein the resin composition has a powder such as aluminum, copper, silver or calcium titanate, as shown in Japanese laid-open patent publication NO. 60-458680. Finally, methods for pretreating with porous silicon dioxide, which can encapsulate the dyestuff, or introducing the resin mixed with silicon dioxide into the surface of polyester woven and knitted fabrics are disclosed in Japanese laid-open patent publication No. 2-216262.
However, the above mentioned processes suffer from a number of problems such as,
(a) It is expensive to add new process steps to the coat-finishing process or to localize a kind of coating resin and to mix the resin with an inorganic materials.
(b) The quality of goods is lost by decreasing the drapability of coated fabrics.
(c) The degree of confidence in production is decreased since the process of anti-migration coating is complicated and great care must be taken in the mixing process of the resin and the coat-finishing process.
In Japanese laid-open patent publication No. 61-252383, the basic concept to obtain good anti-migration properties is by coupling dyestuffs with a tannin compound to slow down the mobility of the dyestuffs in coating layer. However, it is expensive to treat the fabric with synthetic tannin and tannic acid since a special wetting process is necessary and the productivity is lowered by adding this new process step.
Moreover, the wetting treatment with tannin compound suggested in the above disclosure is a known method which is generally used for the improvement of color-fastness to washing of fiber goods dyed with acid-dyes, reactive dyes and partial basic dyes. But this treatment is known to be not effective or only slightly so in the case of disperse dyes.
Japanese laid-open patent publication No. 61-19876 is a method of preventing migration by weakening the affinity between the dyestuffs and the coating resin by coating an N-alkoxydimethylpolyamide resin, in that the degree of substitution of alkoxydimethyl groups is 5-40 mole %, on polyester woven and knitted fabric. However, this coating resin is more expensive than the existing urethane or acrylic resin and has an undesirable feel in use.
Japanese laid-open patent publication No. 60-39479 is a method of preventing migration of the dyestuffs to the coating layer by forming a coating layer of hydrophilic amino acid resin having poor affinity for disperse dyes on both sides or one side of the fabric. The concept of this reference is similar to the above-mentioned Japanese laid-open patent publication No. 61-19876 and it is expensive to form the coating layer of the special resin having such anti-migration properties and the productivity is lowered by adding a special process step.
Japanese laid-open patent publication No. 60-45680 is a method to obtain an anti-migration property by coating with a non-uniform resin composition which is composed of 0.5-50 weight %, based on the weight of resin. This anti-migration property is due to the effect of the metal powder which is distributed in the coating layer.
However, in order to obtain an anti-migration property, it is necessary to obtain a uniform coating layer of micro-powder by using the non-uniform composition composed of micro-powder and resin, but it is impossible to form a uniform coating layer by this method and the unique texture of the fabrics is damaged.
In Japanese laid-open patent publication No. 2-216262, the anti-migration property is obtained by encapsulating the migratory disperse dyes with porous silicon dioxide, which is introduced into the coating layer or into the fabrics. But it is difficult to mix the organic resin with inorganic powder uniformly, as in the above-mentioned Japanese laid-open patent publication No. 60-45680. It is also difficult to obtain a uniform coating layer and the confidence in the product may be low, since as the content of silicon dioxide in the coating resin is increased, the rate of viscosity increase is rapid and the viscosity is greatly variable with time after the resin is mixed.
In Japanese laid-open patent publications No. 1-207475 and 3-45782, coating is carried out after the anti-migration property is imparted to the dyed polyester fabrics by the anti-migration polymerization film or surface modification by treatment with low temperature plasma. But, the cost of equipment for the low temperature plasma process is very high and the process is not practical due to the poor product confidence and to the addition of special process steps.